Efficacy of postmilking disinfection with benzyl alcohol versus lodophor in the prevention of new intramammary infections in lactating cows.

Five Michigan dairy herds participated in a split-herd study to compare the efficacy of two postmilking teat dips in the prevention of new intramammary infections (IMI) in lactating cows. Three hundred seventy cows were assigned to 4% benzyl alcohol, and 387 cows were assigned to 1% iodophor germicidal teat dip. The teat dips were applied by directly immersing the teats immediately after milking. Once a group was assigned to a teat dip, cows in that group maintained on that same teat dip throughout the trial. Total new IMI numbered 254 and 201 for cows treated with benzyl alcohol and iodophor germicidal teat dip, respectively. Staphylococcus spp. (52.0%), Staphylococcus aureus (20.1%), and Corynebacterium bovis (12.2%) were the predominant pathogens that caused new IMI in cows treated with benzyl alcohol. Staphylococcus spp., Staph. aureus, and C. bovis, respectively, were the pathogens responsible for 69.7, 12.4, and 4.5% of the new IMI in cows treated with iodophor. The incidences of new IMI caused by Staph. aureus (0.66 new IMI/100 milking quarters per mo), C. bovis (0.38 new IMI/100 milking quarters per mo), and all pathogens (3.15 new IMI/100 milking quarters per mo) were higher in cows treated with benzyl alcohol than in cows treated with iodophor (0.29, 0.11, and 2.35 new IMI/100 milking quarters per mo, respectively). Incidence of new IMI did not differ between groups for other pathogens. One percent iodophor prevented new IMI caused by contagious pathogens more effectively than did benzyl alcohol.